The present invention relates generally to the structural configuration of a truck body having at least one roll-up door for loading and unloading cargo therethrough, and more particularly to a sub-frame assembly which provides a high level of strength, ease of fabrication, and efficient connection of structural components. It will be understood that truck body, as used herein, also includes trailers and the like.
The addition of one or more roll-up doors to a truck body adds significantly to the efficiency of loading and unloading cargo for the truck body. If a roll-up door is located on a longitudinal side wall of a typical truck body, a large opening is provided through which much of the cargo in the truck body can be directly accessed without having to rearrange the load. The use of a roll-up door also allows the truck body to be parked and unloaded in smaller areas where traditional hinged doors, which require considerable space for swinging open the doors, could not be used. For delivery services such as beverage distributors, which may need to stock a large variety of different beverage products at each retail beverage outlet which is served by the distributor, truck bodies having roll-up doors are particularly beneficial and save much time which would otherwise be lost in rearranging cargo or parking some distance away in a more open space.
The use of large roll-up doors, however, significantly reduces the structural rigidity of the truck body, and places additional stresses on the corner connections of the truck body. Because the large opening in the side wall of the truck body eliminates at least some horizontal structural members which would otherwise provide strength and rigidity to the body, the corner connections of the truck body must therefore withstand greater loads. Consequently, manufacturers and purchasers of truck bodies with roll-up doors have experienced relatively high rates of failure in the corner connections of truck bodies with roll-up doors, particularly where the roll-up door is located on a longitudinal side wall of the truck body. In order to save weight, many of the structural components in truck bodies are typically aluminum, and in a large number of cases, particularly for beverage-type truck bodies, all structural components are aluminum. The use of lighter-weight aluminum components allows the truck body to carry a larger payload of cargo, but may increase the vulnerability of certain structural components to fracture and fatigue.
Furthermore, having a roll-up door or doors extending the entire length of one or both side walls of the truck body, which is a desirable arrangement providing the greatest access to the interior of the truck body, results in a roll-up door track being adjacent to one or more corners of the truck body, thereby requiring that each such track be incorporated in the respective sub-frame upper corner assembly to securely anchor it. Including a door track in an upper corner assembly adds considerable complexity to the assembly, which also typically includes a gusset plate, a spacer shim, and a surface for welding a radius header thereto. The time and expense of fabricating the corner assembly increase significantly when a roll-up door track must be incorporated in the truck body.
In conventional truck bodies, the structural members meeting at the upper corners are riveted to a relatively lightweight aluminum corner piece. This arrangement does not provide a durable, high strength connection, and is prone to structural failure. In conventional truck bodies with roll-up doors, the various parts incorporating the door track, gusset place, spacer shim, and exterior corner piece are separately fabricated and then welded together. This composite assembly is butt-welded to the corner post, top rail, and other structural members of the truck body. The fabrication and connection of this type of assembly is difficult, time-consuming, and costly. Moreover, given the large number of butt-welded joints in the assembly and in its connection to the structural members of the truck body, the strength of the assembly is not high, and structural failures are common.
In a different field, prior art patents show the use of corner castings in containers intended for combined overland and marine transportation of goods, as disclosed in Taintlinger U.S. Pat. No. 3,044,653, Durkin U.S. Pat. No. 4,650,381, Durkin U.S. Pat. No. 4,986,705. These corner castings serve specialized purposes and have a highly specialized form, however, in that they protrude outwardly from the rest of the structure of the container and are provided with a type of keyhole aperture for connection with a grappling device that includes a rotating pin having projecting lugs. The entire container may be engaged by the grappling device and hoisted by a lifting mechanism, and then stacked with other containers so that the protruding corner castings of each container are in contact with the protruding corner castings of containers stacked either above or below. These prior art references, which do not incorporate roll-up door openings in the containers involved, do not disclose advantages which would overcome the problems in conventional truck bodies with roll-up doors.
In accordance with the present invention, a sub-frame assembly for a truck body having a roll-up door is provided which possesses a high degree of structural strength, which is easy to fabricate, and which is easily connected to the structural frame of the truck body.